Network/Socket Programming in Java. Rajkumar Buyya

Transcription

1 Network/Socket Programming in Java Rajkumar Buyya

2 Elements of C-S Computing a client, a server, and network Client Request Result Network Server Client machine Server machine

3 java.net Used to manage: URL streams Client/server sockets Datagrams

4 Part III - Networking ServerSocket(1234) Output/write stream Input/read stream Socket( , 1234) Server_name: manjira.cs.mu.oz.au 4

5 Server side Socket Operations 1. Open Server Socket: ServerSocket server; DataOutputStream os; DataInputStream is; server = new ServerSocket( PORT ); 2. Wait for Client Request: Socket client = server.accept(); 3. Create I/O streams for communicating to clients is = new DataInputStream( client.getinputstream() ); os = new DataOutputStream( client.getoutputstream() ); 4. Perform communication with client Receiive from client: String line = is.readline(); Send to client: os.writebytes("hello\n"); 5. Close sockets: client.close(); For multithreade server: while(true) { i. wait for client requests (step 2 above) ii. create a thread with client socket as parameter (the thread creates streams (as in step (3) and does communication as stated in (4). Remove thread once service is provided.

6 Client side Socket Operations 1. Get connection to server: client = new Socket( server, port_id ); 2. Create I/O streams for communicating to clients is = new DataInputStream( client.getinputstream() ); os = new DataOutputStream( client.getoutputstream() ); 3. Perform communication with client Receiive from client: String line = is.readline(); Send to client: os.writebytes("hello\n"); 4. Close sockets: client.close();

7 A simple server (simplified code) import java.net.*; import java.io.*; public class ASimpleServer { public static void main(string args[]) { // Register service on port 1234 ServerSocket s = new ServerSocket(1234); Socket s1=s.accept(); // Wait and accept a connection // Get a communication stream associated with the socket OutputStream s1out = s1.getoutputstream(); DataOutputStream dos = new DataOutputStream (s1out); // Send a string! dos.writeutf( Hi there ); // Close the connection, but not the server socket dos.close(); s1out.close(); s1.close(); 7

8 A simple client (simplified code) import java.net.*; import java.io.*; public class SimpleClient { public static void main(string args[]) throws IOException { // Open your connection to a server, at port 1234 Socket s1 = new Socket(" ",1234); // Get an input file handle from the socket and read the input InputStream s1in = s1.getinputstream(); DataInputStream dis = new DataInputStream(s1In); String st = new String (dis.readutf()); System.out.println(st); // When done, just close the connection and exit dis.close(); s1in.close(); s1.close(); 8

9 Echo Server Client.. //client.java: client interface to server import java.io.*; import java.net.*; public class client { int port_id; String server; Socket slink; DataOutputStream os; DataInputStream is; DataInputStream kbd; public client( String args[] ) { server = args[0]; port_id = Integer.valueOf(args[1]).intValue(); try { slink = new Socket( server, port_id ); os = new DataOutputStream( slink.getoutputstream() ); is = new DataInputStream( slink.getinputstream() ); kbd = new DataInputStream( System.in );

10 Echo Server Client.. catch( UnknownHostException e ) { System.err.println( "Don't know about host: " ); System.exit(1); catch( IOException e ) { System.err.println( "Could not get I/O for the connection to "+server); System.exit(1); void communicate() { while(true) { try { System.out.print("Enter Input <end to stop>: ");

11 Echo Server Client.. if( line.equals("end") ) { os.close(); is.close(); slink.close(); break; String line2 = is.readline(); System.out.println("Output: "+line2); catch( IOException e ) { System.out.println(e); public static void main( String [] args ) { if( args.length < 2 ) { System.out.println("Usage: java client server_name port_id" ); System.exit(1);

12 Echo Server... // server.java: echo server import java.io.*; import java.net.*; public class server { // public final static int PORT = 4779; public static void main( String [] args ) { ServerSocket server = null; DataOutputStream os = null; DataInputStream is = null; boolean shutdown = false; if( args.length < 1 ) { System.out.println( "Usage: java server port_num" ); System.exit( 1 ); int PORT = Integer.valueOf(args[0]).intValue();

13 Echo Server... catch( IOException e ) { System.err.println( "Could not get I/O for the connection to: "); while(!shutdown) { if( server!= null ) { try { Socket client = server.accept(); System.out.println("Connected"); InetAddress cip = client.getinetaddress(); System.out.println( "Client IP Addr: "+cip.tostring()); is = new DataInputStream( client.getinputstream() ); os = new DataOutputStream(

14 Echo Server... if( line.startswith("end" ) ) { shutdown = true; break; os.writebytes(line.touppercase()); os.writebytes("\n"); System.out.println(line); is.close(); client.close(); catch( UnknownHostException e ) { System.err.println( "Server Open fails" ); catch( IOException e ) { System.err.println( "Could not get I/O for the connection

15 Echo Server System.out.println( "Server Down" ); try { server.close(); catch(ioexception e) {

16 Threads in Action... Multithreaded Server Client Process Server Process Server Threads Client Process User Mode Message Passing Facility Kernel Mode

17 Client/Server Computing Rajkumar Buyya

18 Client Server Definition server software accepts requests for data from client software and returns the results to the client

19 Elements of C-S Computing a client, a server, and network Client Request Result Network Server Client machine Server machine

20 Where Operations are Done In CS Relationship most of the application processing is done on a computer (client side), which obtains application services (such as database services) from another computer (server side) in a master slave configuration.

21 CS-Focus is on In client-server computing major focus is on SOFTWARE

22 Application Tasks User Interface Presentation Logic Application Logic Data Requests & Results Physical Data Management

23 Client (dumb) - Server Model Client Keystroke Server Presentation Logic Network Application Logic Displays DBMS

24 True Client-Server Model Client Presentation Logic Keystroke Processed Results Network Server Application Logic DBMS

25 Distributed Client-Server Model Client Application Logic Presentation Logic Processed Queries Processed Results Network Server Application Logic DBMS

26 Client-server computing is distributed access, not a distributed computing.

27 RPC Look and Feel like Local Calls results= bar(arguments) calling procedure results= called bar(arguments) procedure calling procedure (client) arguments results results= bar(arguments) called procedure (client) Local Procedure Call arguments client stub network transport request message results reply message Network Remote Procedure Call results arguments server stub network transport reply message request message

28 Flow Control in a Sychronous RPC Client Machine Server Machine Service Daemon Listening Client Program Client Waiting RPC Call with Request Network return ( ) reply Invoke Service Service Call return() answer Service Executes Request Completed May be the same machine

29 Multithreaded Server Client Process Server Process Server Threads Client Process User Mode Message Passing Facility Kernel Mode

30 Categories of Servers File Server Data Server Compute Server Database Server Communication Server Video Server

31 File Server File Servers manage a work group s application and data files, so that they may be shared by the group. Very I/O oriented Pull large amount of data off the storage subsystem and pass the data over the network Requires many slots for network connections and a large-capacity, fast hard disk subsystem.

32 Compute Server Performs Application logic processing Compute Servers requires processors with high performance capabilities large amounts of memory relatively low disk subsystems By separating data from the computation processing, the compute server s processing capabilities can be optimized

33 Data Server Data-oriented; used only for data storage and management Since a data server can serve more than one compute server, compute-intensive applications can be spread among multiple severs Does not prefer any application processing Performs processes such as validation, required as part management function. logic data of the data Requires fast processor, large amount of memory and substantial Hard disk capacity. Data Server Compute Server

34 Database Server Most typical use of technology in client-server Accepts requests for data, retrieves the data from its database(or requests data from another node)and passes the results back. Compute server with data server provides the same functionality. The server requirement depends on the size of database, speed with which the database must be updated, number of users and type of network used.

35 Communication Server Provides gateway to other LANs, networks & Computers Server & internet server Modest system requirements multiple slots fast processor to translate networking protocols

36 Internet Server Internet Server PC client Local Area Network UNIX workstations

37 Distributed processing application connects to remote database S Q L * Forms SQL *Net TCP/IP UNIX Server Distributed database application connects to local database which connects to remote database SQL *Net TCP/IP SQL * Forms SQL *Net TCP/IP ORACL E ORACLE Database Configurations

38 Client-Server Waves Ethernet era client/server Intergalactic era client/server First Wave Second Wave Third Wave File servers groupware Database servers TP monitors Distributed objects

39 The Client/Server Infrastructure Client Middleware Server Service Specific SQL/IDAPI TxRPC Mail ORB Objects GUI/OOUI DSM Groupware DSM Operating System SNMP CMIP DME Directory Security Distributed file RPC NOS Messaging Transport Stack Peer-to-peer NetBIOS TCP/IP IPX/SPX SNA TP monitor DBMS DSM Operating System